The present invention relates to a stator and a rotating electric machine such as a motor or a generator that employs the stator, and more particularly to a shape of a stator core.
In a stator for a rotating electric machine such as a motor, a generator, or a motor/generator used in an automobile or the like, the stator is normally formed by disposing coil conductors linearly in slots provided parallel to an axial direction of a stator core and causing remaining portions of the coil conductors to project from an axial end surface of the stator core. The portions that project from the axial end surface of the stator core serve as coil end portions that are not used in formation of a magnetic circuit, and are therefore wasteful portions that do not affect output characteristics.
For example, in an IPM (interior permanent magnet) motor described in Japanese Patent Application Publication No. JP-A-2008-148482, a portion of a lead wire of a coil end portion gradually increases in diameter from an end surface of a stator core so as to be positioned on an outer peripheral side of an outer peripheral side bottom portion of a slot in the stator core. To achieve this, in Japanese Patent Application Publication No. JP-A-2008-148482, the axial end surface of the stator core must be positioned further toward an axial inner side than a position at which the lead wire begins to increase in diameter, leading to a reduction in the axial length of the stator core and a reduction in the volume of the stator core for forming a magnetic circuit. Therefore, to improve the output characteristics, the axial length of the stator must be increased.
In an alternating current motor according to Japanese Patent Application Publication No. JP-A-2004-159476, for example, an auxiliary core formed by stacking electromagnetic steel plates is added to a tip end portion and an outer peripheral portion of the teeth of a stator core such that the length of a rotor is increased by an amount corresponding to the added auxiliary cores. By adding the auxiliary cores to the coil end portions, which are wasteful regions that do not affect the output characteristics, torque generated by the motor is increased without increasing the length of a winding.
However, Japanese Patent Application Publication No. JP-A-2004-159476 describes a technique relating to a stator formed by winding armature windings around the tooth portions of the stator core in a so-called concentrated winding condition. Therefore, even though the auxiliary cores are provided on the inner peripheral portion and outer peripheral portion of the coil end portion, the auxiliary cores are not provided on the tooth portions. Hence, it is impossible to supply sufficient magnetic flux to the rotor in the portions provided with the auxiliary cores, and as a result, the output characteristics cannot be sufficiently improved.
Further, in a stator for a rotating electric machine according to Japanese Patent Application Publication No. JP-A-2003-199267, for example, a step-cut portion is formed in a stator core in a circumferential position where a current phase of a coil on an inner diameter side axial end portion of the stator core varies. In so doing, a large temperature increase based on eddy current loss is reduced, leading to a reduction in a maximum value of a temperature increase distributed in the circumferential direction.
However, the technique described in Japanese Patent Application Publication No. JP-A-2003-199267 is only intended to reduce large temperature increases based on eddy current loss, but not intended to improve the output characteristics of a motor or the like formed by a stator core. Therefore, the output characteristics cannot be improved by the technique described in Japanese Patent Application Publication No. JP-A-2003-199267.